The Presence and Significance of A-Waves—A Retrospective Review of 679 Patients

Abstract

Purpose: A-waves are late responses that have been reported in healthy individuals and patients with neurologic conditions. The mechanism(s) responsible for their generation and their clinical significance are not fully understood. The aim was to better characterize A-waves.Methods: A retrospective study was conducted in a high-volume Neurophysiology Department in a tertiary hospital in Melbourne, Australia. Consecutive neurophysiological tests including F-wave studies performed between July 2017 and September 2018 were reviewed to identify A-waves. Patients' characteristics and neurophysiological diagnoses were recorded.Results: A total of 679 patients were included in the analysis and a total of 2,730 nerves were studied. A-waves were most commonly found in tibial nerves, followed by peroneal, median, and ulnar nerves. A-waves were seen in 39.4% of individuals with otherwise normal nerve conduction studies and 39.1% of individuals with entrapment neuropathy. They were most seen in demyelinating neuropathy (85.7%), followed by mixed neuropathy (73.3%), anterior horn cell disease (66.7%), axonal neuropathy (61.2%), and radiculopathy (53.1%). Most patients with demyelinating neuropathy had multiple A-waves (61.9%), but these were also seen in 15.2% of individuals with otherwise normal nerve conduction studies and in 40% of those with other neurologic conditions. A-waves were more often seen in individuals older than 60 years.Conclusions: A-waves are commonly seen in symptomatic individuals with otherwise normal nerve conduction studies and individuals with various neurologic conditions but are more commonly found in nerves with otherwise abnormal electrophysiological testing. A-waves are most seen in tibial nerves. Multiple A-waves were more commonly seen in demyelinating neuropathy than other conditions.

Guillain-Barré Syndrome Mimicking Lumbar Spinal Stenosis with Segmental Weakness in L5-S1 Myotomes

“…Multiple A waves also supported the diagnosis of GBS. Several studies have shown that the finding is a relatively sensitive marker of acute phase GBS (64%-93%) and is rarely seen in LSS (5.8%) (10). Furthermore, tibial SEPs also prompted us to suspect GBS in Case 2 by identifying a severe conduction delay at the nerve root level, which we previously reported in chronic inflammatory demyelinating polyneuropathy, another immune-mediated demyelinating neuropathy (11).…”